The present invention relates to a control system for an electric power steering system, and more particularly to a control system for estimating a driver torque based on a model based estimation and for disabling controlled velocity return.
An electric power steering (EPS) system may employ a torque sensor located between a steering column and a rack and pinion assembly. The torque sensor can measure the torque applied at the pinion and also serve as an approximation of the input torque applied to the steering wheel by the vehicle operator (e.g. driver). The output of the torque sensor may be used in calculations to determine an amount of assist torque provided by the motor.
Although the torque sensor can approximate the driver torque during steady state operations, the torque sensor measurement typically deviates from the driver torque during dynamic transients or during large rack force disturbances, such as when a driver releases the steering wheel, or when a driver subjects the vehicle to driving on a bumpy road, for example. A driver torque sensor can be added on the steering wheel to allow for an accurate measurement at an increased cost. Accordingly, it is desirable to accurately estimate a driver torque in electric power steering system.